1. Field of the Invention
This invention relates to a shutter device and more particularly to a shutter device of the kind arranged to perform opening and closing actions respectively with different shutter blades.
2. Description of the Related Art
The shutter devices of cameras include a kind having two light blocking members which are arranged to open and close an aperture of a lens respectively with a plurality of shutter blades, for example, as disclosed in U.S. patent application Ser. No. 08/287,846, filed Aug. 9, 1994. The shutter device of this kind is arranged as follows. In response to a shutter release operation on a camera, the shutter blades of one (first) light blocking member are moved from their closed positions at which a lens aperture is closed to their fully open positions at which the lens aperture is fully opened, and the shutter/diaphragm blades of the other (second) light blocking member are moved from their fully open positions to their closed positions. Compared with a case where a single light blocking member is to be moved in such a way as "the closed position.fwdarw.the fully open position.fwdarw.the closed position" and particularly where the light blocking member is to be moved by causing a stepping motor to make normal rotation.fwdarw.to stop rotating.fwdarw.to make reverse rotation, this arrangement permits an increase in shutter speed. The increased shutter speed makes it possible, for example, to sufficiently blur a background in contrast with a main object of shooting or to bring the exposure interlocking range of daylight synchronized flashing closer to that of flash photography for a dark place.
In the case of the above-stated shutter device, the opening action of the first light blocking member and the closing action of the second light blocking member are arranged to be almost simultaneously carried out. The acting positions of the two light blocking members are controlled in such a way as to have their positions come to coincide with each other at a point where the aperture area of the lens corresponds to an aperture value set beforehand. In addition to that, exposure time is controlled by varying the acting speeds of the two light blocking members. The so-called aperture priority exposure control is thus carried out.